Financial Instruments Owned and Pledged as Collateral at Fair Value, Securities Purchased Under Agreements to Resell and Securities Sold Under Agreements to Repurchase - Additional Information (Detail) - 6 months ended Jun. 30, 2015	Total
Banking and Thrift [Abstract]
Securities average estimated maturity period (in years)	1 year 1 month 10 days
Confidence Level Value At Risk	98.00%
Value At Risk Threshold	0.10%